Conventionally, materials showing a high dielectric property have been used for electric power applications and telecommunication device applications.
In electric power applications, it is known that the materials are used as electric field-relaxing members of connection portions and terminal portions of electric cables.
In telecommunication device applications, there is a problem of electric noise as a cause of data errors of integrated circuits. In order to suppress the influence of electric noise, there is known a method in which the electric noise may be removed by providing a capacitor having a large electric capacity on a printed circuit, and downsizing and high functionality of electronic parts can be realized by using the high dielectric material as a material of capacitors.
As base materials used for these applications, organic rubbers represented by EPDM and thermosetting resins represented by an epoxy resin are known. Furthermore, recently, high dielectric rubber materials having an excellent weather resistance are being developed by blending a high dielectric substance into a silicone rubber having an excellent weather resistance.
As the high dielectric substance to be blended into the base materials, dielectric ceramics such as a metal oxide or barium titanate, and carbon black are known.
The prior art patents in which the high dielectric substance is blended into the base materials are as follows.
In the invention of JP-A 2003-331653, there is described a silicone rubber composition for electric power connecting portions obtained by blending a composite oxide such as a solid solution of zinc oxide, aluminum oxide as the high dielectric substance, into a silicone rubber as the base material.
In the invention of JP-A 2006-1989, there is described a high dielectric elastomer composition in which a high dielectric ceramic powder is blended into various elastomers.
In the invention of JP-A 5-94717, there is described a composite dielectric material in which porous inorganic dielectric particles including secondary particles obtained by gathering primary particles are dispersed in a resin, and it is also described that the secondary particle is a particle obtained by the primary particles bonded to each other by sintering.
In the invention of JP-A 9-31244, there is described a high dielectric elastomer composition containing composite fibers such as a fibrous material of metal salt of titanic acid. There is also described that in the composite fiber, a molar ratio (Ti/M) between a metal M (Ba, Sr, Ca, etc.) and Ti is in the range of 1.005 to 1.5.
In the invention of JP-A 2003-138067, there is described a high dielectric rubber composition into which barium titanate is blended.
The prior art patents in which a carbon-based material is blended into the base materials are as follows.
In the invention of JP-A 8-22716, there is described a high dielectric insulating rubber material in which a furnace-based carbon black is blended into an ethylene-propylene rubber or an ethylene-propylene-diene rubber.
In the invention of JP-A 2006-290939, there is described a high dielectric elastomer composition in which a dielectric ceramic and a carbon black are blended into styrene-based and olefin-based elastomers.